The present invention generally relates to audio signal amplifiers, and more particularly to an audio signal amplifier for obtaining an output audio signal from an electromagnetic transducer as a signal current as large as possible and for amplifying the obtained audio signal.
Generally, as pick-up cartridges used in record players, there are electromagnetic type pick-up cartridges such as the moving iron (MI) type, and moving coil (MC) type, and moving magnet (MM) type. Conventionally, an audio signal obtained from such an electromagnetic type pick-up cartridge is supplied to a preamplifier for voltage amplification. Particularly, in the case of the MC type pick-up cartridge which produces an output voltage in the order of 1/10 the output of the MI type or MM type pick-up cartridge, the output audio signal is stepped up by approximately 10 times by a stepup transformer or a head amplifier, before the output audio signal is supplied to the preamplifier for further voltage amplification.
Thus, the output audio signal produced from the above mentioned electromagnetic type pick-up cartridge is conventionally subjected to a direct voltage amplification. As a result, the output audio signal is affected by a magnetic non-linear characteristic inherent to the electromagnetic type pick-up cartridge, and there are problems in that the audio signal is distorted especially in the low frequency range and the tone quality is deteriorated.